Assessment of Function, Structure and Working Memory in Adolescents with a Recent Diagnosis of an Eating Disorder

Body, weight and shape related obsessions and ruminations are characteristic traits of individuals with eating disorders (ED) that are found to predate the onset of the disorder. Individuals with chronic ED display altered neural activation in response to food stimuli, and are reported to have volumetric differences compared to healthy individuals, which is likely an effect of prolonged starvation. ED individuals are also seen to dispose an attentional bias to food stimuli, even when perceived sub-consciously, which are reported to interfere with cognitive tasks, including working memory (WM). However, whether the differences in neural activation and structure are present in adolescents with a recent ED diagnosis is not known. In paper I we describe how images of high- and low-calorie foods resulted in greater responses in the prefrontal circuitry in ED adolescents compared to healthy controls (HC). Obsessive-compulsive symptoms in ED individuals were associated with prefrontal circuitry and cerebellar activation, whereas faster reaction times to the WM were associated with greater superior frontal gyrus activity. The findings indicate that ED cognitions may be linked to WM abilities, both of which are associated with frontal cortex functioning. WM performance is examined further in paper II, where we found that the presence of subliminal food images were seen to disrupt WM performance in terms of slower reaction times and less correct responses in ED but not HC. The WM interference was associated with increased activity in the parietal and superior temporal cortex. WM interference caused by subliminal food stimuli may reflect a pre-attentive bias to food in adolescents with ED, which could be a risk factor for further development of an ED. The structural differences in brain volume between adolescents with ED and HC were examined in paper III. ED symptoms were found to be associated with volume differences in insular cortex and superior temporal gyrus, whereas obsessive-compulsive symptoms were associated with reduced volumes in the putamen and cerebellum. These volumetric differences in regions implicated in restraint, obsessions and WM are likely to precede structural variations caused by starvation as seen in chronic ED’s. Connectivity from these regions, in addition to other regions believed to be implicated in ED, was studied in paper IV. Fronto-parietal regions as well as the insula showed increased connectivity in ED, whereas connectivity from the mesolimbic reward regions did not differ from HC. Regions with increased connectivity in ED are involved with self-awareness, body image and ED related ruminations, connections that could influence how one’s body is perceived. In conclusion, the studies included in this thesis describes changes in functional activity, connectivity and brain volume in regions involved with ED cognitions, eating behaviour, and body image in adolescents recently diagnosed with an ED